How Does Blender Voxel Data Work?
First off, that's not ASCII; this is merely a misinterpretation of the raw data. The actual format can be figured out from Blender source files render/intern/include/voxeldata.h and render/intern/source/voxeldata.c together with blenlib/intern/voxel.c. The format is used for 3-dimensional textures. 

The header is read by read_voxeldata_header(), and consists of four ints: the X, Y and Z dimensions, as well as the number of frames. There's no code to handle endianness nor size variations, so the files aren't portable across platforms. Most current platforms will store these as 32-bit little endian. 

Next come the frames, in order. Each frame is also stored in raw memory format, as X*Y*Z floats; this will typically be IEEE 754 single precision (32 bit) values. 

Within each frame, the order of the voxels is defined in the sampling functions. They use a macro named BLI_VOXEL_INDEX to perform the lookup, defined in blenlib/BLI_voxel.h. It shows that the order is along X axis first, then Y axis, then finally Z axis. 

The raw 8-bit format is similar, but has no header, and uses only 8 bit fixed point values; the voxel value is databyte/255.0. This requires the actual dimensions of the voxel to be entered in Blender. 

The image sequence format simply uses a layered group of images, along ascending Z axis. The pixel data gets averaged into a grayscale voxel texture.